tests/ui/deriving/deriving-default-enum.rs

   1 // run-pass
   2
   3 // nb: does not impl Default
   4 #[derive(Debug, PartialEq)]
   5 struct NotDefault;
   6
   7 #[derive(Debug, Default, PartialEq)]
   8 enum Foo {
   9     #[default]
  10     Alpha,
  11     #[allow(dead_code)]
  12     Beta(NotDefault),
  13 }
  14
  15 // #[default] on a generic enum does not add `Default` bounds to the type params.
  16 #[derive(Default)]
  17 enum MyOption<T> {
  18     #[default]
  19     None,
  20     #[allow(dead_code)]
  21     Some(T),
  22 }
  23
  24 fn main() {
  25     assert_eq!(Foo::default(), Foo::Alpha);
  26     assert!(matches!(MyOption::<NotDefault>::default(), MyOption::None));
  27 }